Signaling system for party telephone lines



June 6, 1933. R. c. BRADFORD 1,912,510

' aIGNALING SYSTEM FOR PARTY TELEPHONE LINES Filed Jan. 7, 1932 INVENTOR if. C. flmzfloicd BY ATTORNEY Patented June 6, 1933 UNITED STATES PATENT OFFICE RAYMOND o. BRADFORD; orfrrmnnmoonnnerrcnr, nssrenon. TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, nconronacnron on NEW YORK SIGNALING- SYSTEM FOR PARTY TELEPHONE LINES Application filed January 7, 1932. Serial No. 585,356.

ments of the invention provide for connecting high impedance ringers at the various stations to ground instead of using bridgedringers and also provide means for so dividing the telephone line that ringing may take place over both sides of the line to ground simultaneously instead of ringing over a full metallic circuit. By thus dividing the line to provide separate paths with individual ringers, the number of ringers per circuit is halved and the resistance of the loop over which the station is being rung is cut in two, thereby providing approximately four times as much ringing current through the ringers as would ordinarily be obtained by ringing in the regular way. The arrangements of the invention will tend to improve ringing margins and performance of long multi-party code ringing lines. They will furthermore increase the reliability of operation of the ringers and considerably improve the clarity of the code ringing. A further advantage of the arrangements of the invention resides in the fact that as ringers on both sides of the line are rung simultaneously, if the subscriber takes his receiver from the hook during the j "ments the current from 10 will be applied ringing period, there is no effect equivalent to the cross ringing tendency on divided code ringing lines where only the ringers on one side of the line are supposed to be rung at one time. Furthermore the code rings are not interrupted prematurely inasmuch as the ringers are not shunted by the talking circuit of the subscribers set when the receiver is removed from the hook. Other objects and features of the invention will appear more fully from the detailed description thereof hereinafter given.

The invention may be more fully under-i stood from the following description together trated.

with the accompanying drawing in the Figuresl and 2 of which the invention is illus- Fig. 1 is a circuit diagram embodying a preferred form of the invention. Fig. 2

shows a modification thereof. Similarreference charaoters have been utilized to denote like parts in both figures.

In Fig. 1 is shown a party telephone line L to.which a plurality of subscribers sets might be connected. Ateach subscribers set would be ringing apparatus, such as the ringers 1, 2, 3 and 4. The subscribers set with which ringer 4 is connected is shown in de. tail. The other sets would be substantially SimiIarthereto. Each of these ringers would be connected from the tip or the ring side of the line to ground. The various stat-ions wouldbe rung by sending code signals from the central ofiice to all of the stations simultaneously. Thegenerator 5 is shown at the.

central office for applying alternating current code signals to the line. These signals would operate the alternating current relay 6 which in turnwould operate the relay 7 in accordance with the code signals. The operation of relay 7 would in acCordancewith the code signals'connect the tip and ring sides of line L to separate circuits, each of which would include ballast lamps such as 8 and 9, and thence to acircuit including a source of alter: natingfcurrent 10 connected to ground. Im-

pulses in accordance with the code signals would be sent from source 10 over each side of the line Lsimultaneously and through the findividualringers to ground.

It will be seen that in the above arrangebe at. approximately the same potential;

Hence' when the subscriber at a station removes-the receiver from the switchhook, the

code ringsare not interrupted: prematurely. Furthermore, compared to a system in which the ringers are bridged across the l1ne,'1t-will.

be seen that in the arrangements of the invention the number of ringers will be halved and the resistance of the loop over which the station is being rung is cut in two. The

arrangements of the invention accordingly;

provide approximately four times as much ringing current through the ringers as would ordinarily be obtained by ringing in the regular way.

In Fig. 2 is shown a modification of the arrangements of the invention. Similar reference characters have been utilized to denote like parts with respect to Fig. 1. The arrangements are substantially similar to those heretofore described except that two alternating current relays 16 and 17 are bridged across the line and serve to connect the tip and ring sides of line L to the generator 1Q in response to the code signals from the central oilice.

WVhile the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many and other widely varied forms without departing from the spirit of the invention as defined by the appended claims.

WVhat is claimed is:

1. A party telephone line connecting a plurality of subscribers sets with a central'office,

ringers at each of said subscribers sets'con-' nected from either side of the line to ground, means for applying signal currents to said line at the central office, means responsive to said signal currents for dividing said telephone line, and means for applying signaling currents over the divided sections of said line and through said ringers simultaneously to ground.

2. A party telephone line connecting a plurality of subscribers sets with a central oflice,

ringers at each of said subscribers sets connected from either side of theline to ground, means for applying signals to said line at the central office, relay means connected to said line and responsive to said signals, means controlled by said relay means for connecting the tip and ring sides of said line to a local circuit, and a source of signaling current connected to said local circuit and ground.

3. A party telephone line connecting a plurality of subscribers sets with a central ofiice,

ringers at each of said subscribers sets connected from elther side of the line to ground, means for applying signals to said line at the central oflice, a relay bridged across said line and responsive to said signals, a second relay controlled by said first mentioned relay, a local circuit having a source of signaling current connected thereto and to ground, and means controlled by said second relay for dividing said telephone line into sections and for connecting the tip and ring conductors of one section of said line to said local circuit.

4. A party telephone line connecting a plurality of subscribers sets with a central office,

ringers at each of said subscribers sets. connected from either side of the line to ground, means for applying signals to said line at the 

